Gale Warning 57, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
920 AM PDT FRI OCT 30 2015

.SYNOPSIS...A STRONG FRONT WILL BRING LOCALLY HEAVY RAIN AND WINDY
CONDITIONS AT TIMES THROUGH SATURDAY. THE FRONT WILL DROP SOUTH OF
THE AREA SATURDAY EVENING. STRONG ONSHORE FLOW BEHIND THE FRONT AND
COOLER TEMPERATURES ALOFT WILL GIVE SNOW TO THE MOUNTAINS ON SUNDAY.
A STRONG UPPER RIDGE OFFSHORE WILL BRING DRIER WEATHER NEXT WEEK.

&&

.SHORT TERM...A STRONG JET STREAM IS ENERGIZING A FRONTAL SYSTEM
OVER THE PACIFIC NORTHWEST THIS MORNING AND A GOOD DEAL OF MOISTURE
HAS BEEN ENTRAINED INTO THE FRONT FROM THE CENTRAL TROPICAL PACIFIC.
THE FRONT WILL AFFECT THE AREA IN TWO WAVES...ONE TODAY AND A SECOND
ON SATURDAY.

THE FRONTAL SYSTEM TODAY IS BEING ENHANCED BY THE PASSAGE OF THE
RIGHT ENTRANCE REGION TO A 160 KT JET STREAK THAT IS MOVING ONTO
NORTHERN VANCOUVER ISLAND AND SOUTHERN BRITISH COLUMBIA THIS
MORNING. WHILE MODERATE TO LOCALLY HEAVY RAIN WILL FALL TODAY IN THE
MOUNTAINS TODAY...THE MAIN EFFECT OF THIS FIRST WAVE IS ON THE WIND
FIELD THIS MORNING THROUGH EARLY AFTERNOON. THE PORTLAND TO
BELLINGHAM PRESSURE GRADIENT IS PEAKING AT AROUND 11.6 MB AND
OLYMPIA TO BELLINGHAM AT 5.6 MB THIS MORNING. A WIND ADVISORY WAS
ISSUED FOR THE INTERIOR LOWLANDS FROM ABOUT TACOMA AND SHELTO
NORTHWARD TO THE CANADIAN BORDER UNTIL 3 PM. SOME WIND GUSTS TO 55
MPH HAVE BEEN REPORTED AROUND BELLINGHAM AND THE SAN JUAN
ISLANDS...WHILE GUSTS TO 40-45 MPH HAVE BEEN REPORTED AROUND THE
PUGET SOUND AREA. WINDS WILL SLOWLY RELAX THIS AFTERNOON AS
GRADIENTS TURN MORE WESTERLY.

THE LEFT EXIT REGION TO A SECOND STRENGTHENING JET STREAK WILL MOVE
ACROSS THE AREA ON SATURDAY. THIS WILL REENERGIZE THE FRONT LATE
TONIGHT INTO SATURDAY ACROSS THE AREA AND RESULT IN AN 18 HOUR
PERIOD OF VERY HEAVY RAINFALL IN THE MOUNTAINS AND WINDY CONDITIONS
IN THE LOWLANDS. A QUICK LOOK AT FORECAST PRECIPITATION AMOUNTS FROM
INCOMING MODELS SHOW SIMILAR AMOUNTS AS PREVIOUS MODEL SOLUTIONS.
SEE THE HYDROLOGY SECTION BELOW FOR EXPECTED IMPACTS ON RIVERS. A
FLOOD WATCH REMAINS IN EFFECT FOR THE ENTIRE AREA EXCEPT THE SAN
JUAN ISLANDS AND ISLAND COUNTY. FLOW ALOFT INTERACTING WITH THE
MOUNTAINS AS THIS SECOND JET STREAK PASSES WILL ALSO ENHANCE SOUTH
WINDS OVER THE COAST AND IN THE CHANNELED PUGET SOUND LOWLANDS...SO
A WIND ADVISORY WILL LIKELY BE REQUIRED AGAIN FOR SATURDAY.

THE FRONT WILL DROP SOUTH SATURDAY NIGHT INTO SUNDAY LEAVING THE
AREA IN A COOL UPPER TROUGH WITH STRONG ONSHORE FLOW AND OROGRAPHIC
LIFT. SNOW LEVELS ARE EXPECTED TO DROP TO 3500-4000 FEET AND
MOUNTAIN QPF AMOUNTS APPEAR SUFFICIENT TO PRODUCE HEAVY SNOWFALL
AMOUNTS IN THE MOUNTAINS. A WINTER STORM WATCH WILL LIKELY BE ISSUED
FOR LATE SATURDAY NIGHT INTO SUNDAY IN THE MOUNTAINS WITH THE
AFTERNOON FORECAST PACKAGE.

A STRONG UPPER LEVEL RIDGE WILL BUILD INTO THE AREA FROM THE WEST
STARTING ON MONDAY. THIS RIDGE WILL GIVE DRYING CONDITIONS TO
THE AREA. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...AN UPPER LEVEL
RIDGE WILL NUDGE EAST AND INLAND TUESDAY THROUGH THURSDAY FOR DRY
BUT COOL WEATHER. TEMPS WILL BE A FEW DEGREES BELOW NORMAL WITH
HIGHS NEAR 50 AND LOWS IN THE MID 30S TO LOWER 40S. THE RIDGE MAY
BREAK DOWN LATE NEXT WEEK AS A WEAK WARM FRONT MOVES IN. 33

&&

.HYDROLOGY...MESOSCALE MODELS...WHICH GENERALLY HAVE THE MOST
ACCURATE RAINFALL PREDICTIONS...ARE IN GOOD AGREEMENT ABOUT THE
TIMING AND LOCATION OF HEAVY RAINFALL. THEY ALL SHOW THE HEAVIEST
RAIN OVER THE SOUTH CASCADES WITH A NOTABLE BULLSEYE OVER MOUNT
RAINIER...HEAVIEST TONIGHT AND SATURDAY MORNING. THE OUTLIER BROAD
SCALE MODELS SUCH AS THE EURO AND THE GEM...WHICH PREVIOUSLY HAD
MORE RAIN OVER THE NORTH...NOW SEEM TO BE COMING INTO AGREEMENT
ABOUT A FOCUS OF RAINFALL OVER THE SOUTH CASCADES.

THIS IS THE FIRST HYDROLOGICAL EVENT OF THE SEASON AND RIVERS WILL
RESPOND SLOWER THAN USUAL AND WILL NOT RISE AS FAR AS THEY WOULD
LATER IN THE SEASON. HOWEVER THE CURRENT QPF GIVES MINOR FLOODING ON
SEVERAL RIVERS FROM THE SKAGIT SOUTH TO THE COWLITZ. THE RIVERS
FLOWING OFF MOUNT RAINIER WILL PROBABLY GO HIGHER...SOME TO MODERATE
STAGE. THE CURRENT QPF...WHICH IS A BLEND OF MESOSCALE MODELS...HAS
4-8 INCHES MOST OF THE CASCADES AND OLYMPICS WITH A 10-13 INCH
BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE QUITE HIGH WITH
THIS SYSTEM...AROUND 8000 FEET IN THE SOUTH CASCADES...SO THE VAST
MAJORITY OF PRECIPITATION IN THE MOUNTAINS WILL BE RAIN NOT SNOW.

THE SNOQUALMIE RIVER AT CARNATION IS ALSO FORECAST TO REACH MODERATE
FLOOD STAGE. NO RIVERS ON THE OLYMPIC PENINSULA ARE FORECAST TO
FLOOD YET...WITH THE POSSIBLE EXCEPTION OF THE SKOKOMISH RIVER IN
MASON COUNTY.

HEAVY RAIN IS FORECAST TO END SATURDAY AFTERNOON AS A COLD FRONT
MOVES SOUTH THROUGH THE AREA. THE SNOW LEVEL WILL FALL TO 3000 TO
4000 FEET SUNDAY. BURKE

&&

.AVIATION...A FLAT RIDGE OF HIGH PRESSURE WILL BE REPLACED BY
AN UPPER TROUGH DIVING SWD OVER THE REGION SATURDAY AND SUNDAY. A
SURFACE WARM FRONT LIFTING INTO WRN WA THIS MORNING WILL DISSIPATE
OVER THE AREA DURING THE AFTERNOON. MODERATE TO STRONG W-SW FLOW
ALOFT. STABLE AND MOIST AT ALL LEVELS. THERE WILL BE A COUPLE WAVES
OF STRONG SOUTHERLY WINDS 15-30 MPH WITH GUSTS TO 45-50 MPH ACROSS
THE LOWLANDS TODAY AND AGAIN SATURDAY. WIDESPREAD MVFR CIGS WITH
BRIEF IFR CONDITIONS AT TIMES. RAIN AT TIMES THROUGH THE WEEKEND.

&&

.MARINE...SEVERAL CHANGES WERE MADE TO THE MORNING FORECAST
ISSUANCE. SLY GRADIENTS ARE COMING UP MUCH MORE THAN EXPECTED AND
NEARING 12MB KPDX-KBLI AND NEAR 6 MB KOLM-KBLI. THAT IS USUALLY
SUPPORTIVE OF LOW END GALES WITH GALE WARNINGS NOW UP FOR ALL
INTERIOR WATERS UNTIL 3 PM. WESTERLY GRADIENT IS ALSO STARTING TO
POP IN THE STRAIT WITH GALES POSSIBLE IN THE CENTRAL/E STRAIT.
WARNINGS ARE UP THERE THROUGH 6 PM. SMALL CRAFT REMAINING WATERS.
ANOTHER FRONT WILL TIGHTEN GRADIENTS AGAIN ON SATURDAY WITH SOME
POTENTIAL FOR GALES ACROSS SOME OF THE WATERS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY INTERIOR LOWLANDS FROM TACOMA AND SHELTON
     NORTHWARD TO THE CANADIAN BORDER UNTIL 3 PM PDT THIS AFTERNOON.

     FLOOD WATCH IN EFFECT FOR MUCH OF WESTERN WASHINGTON THIS EVENING
     THROUGH SUNDAY AFTERNOON.

PZ...SMALL CRAFT ADVISORY COASTAL WATERS AND WEST ENTRANCE TO THE
     STRAIT OF JUAN DE FUCA.

     GALE WARNING FOR ALL REMAINING WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS THROUGH SATURDAY
     GRAYS HARBOR BAR.

&&

WWW.WEATHER.GOV/SEATTLE

AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION CAN BE SEEN AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
224 PM PDT FRI OCT 30 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0205 PM     HEAVY RAIN       1 NNE SULTAN            47.87N 121.80W
10/30/2015  M1.23 INCH       SNOHOMISH          WA   TRAINED SPOTTER

            SPOTTER MEASURED 1.23 INCHES OF RAIN OVER 50 MINUTES
            ENDING AT 205 PM PDT.

&&

JSMITH